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Cryptography[]
Cryptography (or cryptology; from the Greek work kryptos meaning "hidden, secret") is the practice and study of hiding information.
ROT-13[]
- Main article: ROT-13
The ROT-13 ("rotate by 13 places") is a simple substitution cipher. ROT13 is a variation of the "Caesar's cipher" (see below).
Applying ROT-13 to a piece of text merely requires examining its alphabetic characters and replacing each one by the letter 13 places further along in the alphabet, wrapping back to the beginning if necessary.
- A becomes N, B becomes O, and so on up to M, which becomes Z.
- Then, the sequence reverses: N becomes A, O becomes B, and so on to Z, which becomes M.
Only those letters which occur in the English alphabet are affected; numbers, symbols, whitespace, and all other characters are left unchanged. Because there are 26 letters in the English alphabet and 26 = 2 × 13, the ROT13 function is its own inverse:
Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ Cipher: NOPQRSTUVWXYZABCDEFGHIJKLM
Caesar's cipher[]
- Main article: Caesar cipher
The Caesar's cipher (also known as the shift cipher or Caesar's code) is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet.
- For example, with a shift of 3, A would be replaced by D, B would become E, and so on.
Shift by 3 (or +3)
Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ Cipher: DEFGHIJKLMNOPQRSTUVWXYZABC
Example:
Plaintext: the quick brown fox jumps over the lazy dog Ciphertext: WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ
Hidden key cipher[]
The Hidden key cipher uses a cipher alphabet which is scrambled methodologically with the use of a key word or phrase. For example, if the word CRYPTO is chosen as the keyword, then the cipher alphabet is created by placing the word at the beginning, and following it with other letters of the alphabet that are not in the keyword.
If the key has repeated letters, then only the first one is used.
Key: CRYPTO
Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ Cipher: CRYPTOABDEFGHIJKLMNQSUVWXZ
Key: BAMBOOZLE
Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ Cipher: BAMOZLECDFGHIJKNPQRSTUVWXY
Combination ciphers[]
In general, it is quite common to use several methods (or ciphers) to encrypt a message. For example, the Caesar cipher can be combined with the hidden key cipher. First a key is used to create the cipher alphabet, then the cipher alphabet is shifted a set number of spaces.
Key: RUNESCAPE
Shift: -5
Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ
RUNESCAPBDFGHIJKLMOQTVWXYZ
Cipher: VWXYZRUNESCAPBDFGHIJKLMOQT
CryptoChallenge 1[]
The following feature quotes from a famous TV family.
Noob[]
ONEG, JVGU $10,000, JR'Q OR ZVYYVBANVERF! JR PBHYQ OHL NYY XVAQF BS HFRSHY GUVATF YVXR...YBIR!
Novice[]
Hint: Positive shift
Z'D CZBV KYRK XLP NYF JZEXCV-YREUVUCP SLZCK KYV IFTBVK & WCVN KF KYV DFFE. NYRK NRJ YZJ ERDV? RGFCCF TIVVU?
Hint: Negative shift
YVP, NV UZUE'K YRMV R DVJJRXV FE FLI REJNVIZEX DRTYZEV NYVE NV CVWK. YFN MVIP FUU.
Intermediate[]
Hint: Combination
Key hint: Solve the three challenges above. The key is in the name.
ZHAP AH RPXQ: RAHO. NHUZS. JZGATUZS.